A common form of a precision resistor is a length of relatively thin resistance wire wound as a multilayer coil on a coil form or bobbin. As is well understood, one disadvantage associated with this form of wire wound resistor is that the multilayer coil has appreciable inductive reactance which is undesirable for many uses of the resistor. Many different coil winding techniques and many different forms of resistor elements have been devised in attempts to minimize the inductive reactance associated with this type of resistor.
It is known in the art to deposit a resistor wire on the adhesive backing of a thin sheet of insulator material and then roll the tape into a tight spiral, or fold it back and forth accordion style before encasing it in a housing. Conventional coil forms that are commonly employed in wire wound resistors are not used. U.S. Pat. Nos. 2,860,220 -- Keeler, and U.S. Pat. No. 3,541,491 -- Worster, disclose resistors manufactured as described above. Furthermore, precision resistors of large resistance values require a very long length of resistor wire. In the manufacture of wire wound resistors, for example, multibobbin coil forms are used. In such multibobbin resistors, the wire is passed through a slot in a common flange between adjacent coils. In the winding of a multibobbin wire resistor, the crossover from a full bobbin to the cylindrical body of an empty bobbin presents no particular problem. However, when working with a relatively wide tape having the thin resistor wire deposited thereon, the crossover presents a problem since the tape must cross over from the outside of the full coil to the inside of the empty spool, and then be wound from the inside to the outside of the spool.
Workers trained to wind conventional wire wound resistors are familiar with and adept in working with coil forms, and if they may continue to apply their skills in winding tape on a bobbin or coil form, a minimum of retraining is required. Additionally, winding directly onto a coil form is considerably simpler than some of the procedures suggested in the above-mentioned patents for making a multicoil resistor.
A further advantage of using a coil form with a tape having resistance wire thereon is that the mechanical support and rigidity provided by the coil form is retained. Also, the relatively stiff connector lead of the coil form are retained.